1. Field of the Invention
The present invention relates to an electrical powered vehicle including power storage devices, and a control method therefor, particularly control for preventing excessive charging and discharging of the power storage device.
2. Description of the Background Art
The technique for suppressing, in an electrical powered vehicle incorporating power storage devices, the charging and discharging caused by excessive power of each power storage device is disclosed, for example, in Japanese Patent Laying-Open No. 2006-094691.
According to this publication, a “slow-changing process” is applied to the deviation between the calculated power and actual power that is input/output by a rotating electric machine to smooth the amount of change in the deviation along the time axis, and the limit value of allowable input/output power with respect to the power storage device is calculated based on the smoothed deviation. When the driving state of the vehicle changes greatly such as in a speed-change state or in a slipping state, the “slow-changing process” is carried out using a time constant smaller than that of the general time constant, whereby the limit value of allowable input/output power with respect to the power storage device is modified rapidly. Accordingly, excessive charging/discharging of the power storage device is suppressed.
In view of the control for an electrical powered vehicle, an overall cooperative vehicle control is now being developed based on communication of data and information between electronic control units (ECUs), each ECU provided individually for each control function, from the standpoint of the processing capability of a control device constituted of an ECU. For example, in an electrical powered vehicle, power consumption by the power running operation and power generation by the regenerative operation of the electric motor for driving the vehicle must be carried out within a power range that can be charged/discharged by the power storage device. Under such circumstances, a configuration may be employed in which an ECU for controlling the electric motor and an ECU for setting the charging/discharging command of the power storage device to manage the entire power balance are provided separately.
Consider the case where the driving state such as the rotational speed is abruptly modified at the electric motor. The sudden change in the power consumption or generated power at the electric motor caused by such abrupt modification may not be immediately reflected in the charging/discharging command for the power storage device. There will be time delay including the time required for communication between the ECUs. Particularly in the case where power is charged/discharged taking into account the power distribution among a plurality of power storage devices, there is the possibility of excessive charging or excessive discharging of the power storage device since the charging/discharging command for each power storage device cannot be corrected rapidly in response to the change in the driving state of the electric motor.